1. Field of the Invention
The present invention relates to a focal point adjustment device and a focal point adjustment method for performing focal point adjustment by a phase-difference AF (Auto Focus) system, based on the output of an image sensor including an imaging pixel and a focal point detection pixel.
2. Description of Related Art
There is known a focal point adjustment device that arrays a focal point detection pixel in a part within a two-dimensional array of imaging pixels to capture a subject image formed by a photographic optical system and also adjusts the focal point of the photographic optical system by a pupil division phase difference method. With the image sensor of this focal point adjustment device, the incident angle to a photoelectric conversion element of the focal point detection pixel of each of a pair of focal point detection light fluxes having passed through different regions on the exit pupil of the photographic optical system varies as the distance from a point where the image sensor intersects with the optical axis of the photographic optical system becomes larger in the light receiving surface of the image sensor, resulting in a decrease in focal point detection accuracy.
Then, in order to solve this problem, there has been proposed a focal point adjustment device adapted to set, in accordance with the image height in the light receiving surface of an image sensor, the positional relationship between a micro lens for pupil division and a focal point detection pixel (see Japanese Laid-Open Patent Publication No. 2009-290157 (hereinafter, referred to as “Patent Literature 1”)).
The device in Patent Literature 1 is capable of reducing an error caused by the image height of a focal point detection pixel. However, because the AF (Auto Focus) characteristics will vary not only with the image height but also with the states of the focal length, focus position, aperture, and the like, of a photographic optical system, correction needs to be performed in accordance with the states of the optical system.
Furthermore, when the focal point adjustment device includes the so-called camera-shake preventing mechanism for driving an image sensor in the plane perpendicular to the optical axis of a photographic optical system in accordance with camera shake in performing camera-shake correction, the device cannot eliminate an error caused by a relative change of an image height due to the movement of the image sensor. In particular, when an image sensor rotationally moves about the rotation center thereof, the movement becomes complicated and it is not easy to eliminate the error.
In addition, for a micro lens provided on an image sensor, in terms of the manufacturing process, a relative positional shift may occur between a portion constituting a light receiving element and a portion constituting a microlens array, and it is also not easy to eliminate an error caused by this relative positional shift.